This waterway, in northwestern South Dakota is
coated with salt along its banks. Researchers at South Dakota Mines are finding
a trend of increasing salinity in the waters of many stock dams and waterways
in South Dakota during the 2021 drought.
A team of research faculty and students at South Dakota Mines has been tracking salinity
content in 70 stock dams across 12 watersheds in two northwestern South Dakota counties
over the past two years. Their study, funded by the Bureau of Land Management, shows
an alarming trend of increasing salinity in the stock dam water during the ongoing
drought of 2021. In some cases, the salt concentrations of the water is high
enough to cause adverse health effects for livestock and wildlife. In a handful
of stock dams, the salinity is high enough to be lethal.
“We hope the information will help the people who
matter the most, and that’s the livestock producers in this scenario,” says
Lisa Kunza, Ph.D., associate professor of chemistry, biology, and health sciences
at South Dakota Mines. “Our producers need decent water to give to their cattle
and this trend could exacerbate the water shortages they are already facing. We
hope our students can foster this collaborative effort to help local ranchers
and land managers understand this problem, know their options, and find
solutions.”
Sampling done by the team of student researchers in
Butte and Harding counties, showed low salinity levels during the wetter years of
2018-2019. But in times of drought, such as the first half of 2021, many stock
dams begin to dry up, and this evaporation caused increased salinity. Researchers
can estimate the amount of salt in water by testing its electrical
conductivity. Water with higher salt content is more conductive. Electrical
conductivity measurements of less than 5,000 microsiemens per centimeter (µS/cm)
are relatively safe water levels for livestock consumption. “This year, we have
seen a 19% increase in stock dams with conductivity over 5,000 µS/cm (none in
2019) and 6% of those stock dams over 11,000 µS/cm. We see salinity increase as
the drought continues and as many of these impoundments dry up,” says Patrick
Kozak, a Ph.D. graduate student at South Dakota Mines who is conducting the
research.
Stock dams are common for livestock producers across
the American West to make sure their animals have access to water. In
northwestern South Dakota alone, there are 77,000 stock dams. These small earthen
dams catch water during rain events and snowmelt in the spring allowing for
water availability through the rest of the year. Many of these dams were
constructed between the 1930’s and 1990’s, and some are abandoned or not being
utilized by the cattle due to water quality.
During droughts the water can dry and up and disappear leaving the
producers without water.
In the Upper Great Plans, stock dams are often
located in soils formed from ancient seafloor. These soils can contain elevated
amounts of remaining salts from the evaporated seawater. These salts are
dissolved and transported downstream to collect in stock dams, riparian areas,
and other low-lying regions. Over time the salts accumulate and become more and
more concentrated. “People are starting to notice white spots and salt crusting
around stock dams and along streams and drainages where it hasn’t been before,
and we are doing this study to get a better understanding of what is
happening,” says Kozak.
The team is looking to expand its research to a broader
area in the Great Plains region. They hope to provide information to help local
ranchers and government land managers to make the best decisions to support and
protect livestock and wildlife.